'PULSE' LED - reporting an Oscillating State e.g. Clock or Step Change (Up or Down).

2-way Toggle Switch. Positions: 'CMOS' 40'xx Series and 'TTL' 74'xx Series, for selecting between the two chip sets.

A 2-way insulated power cable terminating in one Red and one Black crocodile clip for linking to the circuit under test's power supply to ensure a common ground. No battery required.

Logic Probe Case with Red / Black Croc. Clips Power Cable.

Logic Probe Case (open) with Circuit.

The circuit was soldered onto a 9 x 37 hole vero-board which was cut to size using a hacksaw then filed to smooth the edges. This gave 9 fully conducting rows of holed copper. A 'spot face cutter' tool was required to 'halve-drill' holes in the vero-board to stop the whole track row length conducting. For two sides of a IC for example.

Spare 2-way strips of ribbon cable was used to connect the circuit board to the 4 LED's, and 2-way switch. These were covered in insulating tape to stop short circuits between the board and components. The 2-way insulated power cable terminated in the circuit board. And one final wire went to the probe its self.

Preparing the Case

All components were bought from
Maplin Electronics
including the Case [ Maplin Code FT31 - 99p ]. The legends next to the LEDs, Switch, and Logic Probe Name were applied using white transfers. Then set by painting a little varnish over each word using a paint brush. The following holes had to be drilled in the case:

x4 LED Holes for the four RED 5mm LED's. With 5mm LED Clips to hold them in place (cheap chrome bezzels are now available which would look more professional). RED LED's (12p) are generally a few pence cheaper than Green, Orange, or Yellow because of the relative complexities of the manufacturing process. Blue LED's are phenomenally expensive to produce (91p!).

x1 Hole for the toggle switch. Which should be attached using the Hex. Nut and crinkly Shake (to stop the switch loosening after constant use).